Currently, multi-channel audio signals are widely used in various scenarios, such as telephone conference and game. Therefore, coding and decoding of multi-channel audio signals is drawing more and more attention. Conventional waveform-coding-based coders, such as Moving Pictures Experts Group II (MPEG-II), Moving Picture Experts Group Audio Layer III (MP3), and Advanced Audio Coding (AAC), code each channel independently when coding a multi-channel signal. Although this method can well restore the multi-channel signal, a required bandwidth and coding rate are several times as high as those required by a monophonic signal.
Currently, popular stereo or multi-channel coding technology is parametric stereo coding, which may use little bandwidth to reconstruct a multi-channel signal whose auditory experience is completely the same as that of an original signal. The basic method is: at a coding end, down-mixing the multi-channel signal to form a monophonic signal, coding the monophonic signal independently, extracting channel parameters between channels simultaneously, and coding these parameters; at a decoding end, first decoding the down-mixed monophonic signal, and then decoding the channel parameters between the channels, and finally using the channel parameters and the down-mixed monophonic signal together to form each multi-channel signal. Typical parametric stereo coding technologies, such as the PS (Parametric Stereo), are widely used.
In parametric stereo coding, the channel parameters that are usually used to describe interrelationships between channels are as follows: Inter-channel Time Difference (ITD), Inter-channel Level Difference (ILD), and Inter-Channel Coherence (ICC). Theses parameters may indicate stereo acoustic image information, such as a sound source direction and location. By coding and transmitting these parameters and the down-mixed signal that is obtained from the multi-channel signal at the coding end, the stereo signal may be well reconstructed at the decoding end with a small occupied bandwidth and a low coding rate.
However, during the process of researching and implementing the prior art, the inventor of the present invention finds that: By using the conventional parametric stereo coding and decoding method, a problem that processed signals at the coding end and the decoding end are inconsistent exists, and the inconsistency of the coding and decoding signals may cause quality of a signal obtained through decoding to decline.